Following is the standard cleaning procedure and should be applied to any installation of Toray’s MBR system. Please contact our technical support team for cleaning assistant of your MBR system.


Chemical cleaning of membrane elements should be conducted when the trans-membrane pressure rises to excess. Such a pressure increase can be caused when contaminants clog the pores of the membrane surface. The timing of chemical cleaning should be determined as follows:

  • Every 6 months or when the trans-membrane pressure has risen by 5 kPa from its initial operating level at the same permeated water flow rate, whichever earlier.
  • The early chemical cleaning is effective to remove contaminants clogged in the membrane pores.
  • In the case that the trans-membrane pressure raises by 5 kPa within 6 months, observe how many months it takes for the trans-membrane pressure to rise by 5 kPa and conduct chemical cleaning periodically. This measure is effective in prolonging the life of membranes. The cleaning interval may be changed due to different process conditions.

Chemical cleaning is made by CIP (cleaning in place) process as shown on the following graph:

To prevent damage of elements : Back pressure < 1 m H2O

Chemical Agents Used for Chemical Cleaning

For chemical cleaning of element, it is important to select chemicals in accordance with the type of adherent contaminant. Cleaning under inappropriate cleaning conditions or using the wrong chemicals may cause poorer filtration performance or damage to the element. Select chemicals suitable for each contaminant. The following table shows suitable chemicals and standard cleaning conditions.

Contaminant Chemical Solution concentration Amount used Hold time
Organic matter Sodium hypochlorite 2,000-6,000 mg/L
 (Effective chlorine concentration)
(pH is about 12)
5 L/element 1 to 3 hours
Inorganic matter Oxalic acid 0.5-1.0wt% 5 L/element 1 to 3 hours
Inorganic matter Citric acid 1-3wt% 5 L/element 1 to 3 hours


Clogging of diffuser holes may lead to uneven air diffusion and membrane clogging. To prevent such clogging, cleaning of the air diffusers is requred at least once a day (it is recommended to automate the air diffuser cleaning process by using automatic valves).

The cleaning is done by the reverse flow sludge from the diffuser hole into the diffuser piping generated by opening the air diffuser cleaning valve and releasing the pressure inside the air diffuser, discharging such sludge by the diffusing air through the branch valve.

Procedure for Air Diffuser Cleaning:

(i) Stop filtration.
(ii) Close V1 valve.
(iii) Open V2 valve. At this step, the sludge liquid comes through the diffuser holes into diffuser piping, and is discharged together with the air.
(iv) Keep V2 valve open for about one (1) minute.
(v) Close V2 valve, and then open V1 valve.
(vi) Clean the other line in the same manner as follows.
(vii) Close V3 valve.
(viii) Open V4 valve. At this step, the sludge liquid comes through the diffuser holes into diffuser piping, and is discharged together with the air.
(ix) Keep V4 valve open for about one (1) minute.
(x) Close V4 valve, and then open V3 valve.
(xi) Restart filtration.

For detailed information on the cleaning process please consult our technical support team and use the procedure described in the instruction manual available on purchase of your MBR module.